The present invention relates to a filter for treating storm water. More particularly, it relates to a filter canister configured for use within a storm water sewer system.
Over the past several decades, the public awareness and concern regarding environmental issues has intensified greatly. To this end, a variety of local, state and federal pollution control agencies have been established to monitor the environment and enforce environmental regulations on individuals, businesses and municipalities. The broad scope of activities encompassed by these agencies illustrates the importance society has placed on controlling potential environmental hazards, including automobile emissions, landfills, industrial emissions, etc.
One extremely important environmental concern is contaminated or wastewater. Contaminated water is generated by many different sources. Regardless of the source, the contaminated water must be processed or xe2x80x9cdecontaminatedxe2x80x9d before allowed to flow into a natural water source, such as a pond, wetland, marsh, stream or river. For example, with industrial applications, wastewater generated by a particular manufacturing plant must, according to state and/or federal regulations, be treated to remove, or at least minimize, toxic or otherwise harmful substances prior to the wastewater being distributed into a city sewer system. Similarly, a city or town""s sewage treatment facility must treat or decontaminate sewage. An additional, although sometimes overlooked, source of potentially toxic wastewater is storm runoff. More particularly, as rainwater drains from yards and driveways to the xe2x80x9cstorm waterxe2x80x9d sewer system, it accumulates a number of materials including grass clippings, fertilizer, pesticides, oil, metals, etc. Left untreated, these metallic, organic and other contaminants are allowed to flow through the storm sewer system to a nearby retention pond, where they can then contaminate the ground water supply and/or promote uncontrolled growth of bacteria or algae, etc., or directly into lakes, streams or rivers where similar problems can occur.
A number of different wastewater treatment methodologies have been developed in recent years. Invariably, the particular technique employed at any one location relates to the type of contaminants otherwise present in the wastewater produced by that location. One typical approach for treating contaminated wastewater is to direct the wastewater through a filtering system. In theory, the filtering system allows relatively xe2x80x9ccleanxe2x80x9d water to flow through while preventing or stopping movement of the contaminant(s). For example, where the wastewater contains rocks, paper or other relatively large objects, the filtering system may include a screening. The screening xe2x80x9ccatchesxe2x80x9d the rocks, paper and other material, while allowing water to flow through. The contaminant material is later physically removed from the screen. Where, however, the contaminants in question are much smaller and/or dissolved into the wastewater, more sophisticated filtering techniques must be utilized.
The general goal behind alternative filtering techniques is to cycle the contaminated water through a filtering medium for which the particular contaminant(s) in question have an affinity. With this configuration, the contaminants attach themselves to the filtering medium, such that xe2x80x9ccleanxe2x80x9d water exits the system. One example is treatment of aqueous solution (such as water) containing cationic metal contaminants. Treatment of a toxic cationic bearing aqueous solution is normally accomplished through the use of a filtering system incorporating an ion exchange resin or medium. Generally speaking, the ion exchange medium acts to adsorb toxic metal cations and/or other toxic cations. In other words, the toxic cations have an affinity for the ion exchange material, which acts to retain or remove the toxic material from the water or other aqueous solution. The ion exchange medium removes the toxic metal cations and replaces them with a more neutral material, such as sodium, oxygen or potassium.
A wide variety of materials are available for use as an ion exchange material. For example, research has been done on the effectiveness of processed peat. Peat is the product of the partial decay of saturated dead vegetation, and is relatively inexpensive. In order for peat to be useful as an ion exchange material, it normally must be sulfonated. This result is typically achieved by treating the peat with a strong sulfonating agent such as sulfuric acid. One example of such a process is described in U.S. Pat. No. 5,314,638 in which peat is first milled into particles less than 1 millimeter in diameter, then hydrolyzed, debituminized, and thereafter sulfonated. While the method described in U.S. Pat. No. 5,314,638 produces a sulfonated peat material with an improved ion exchange capability, the processing itself is quite expensive and produces only a small quantity of material during each processing cycle. Notwithstanding these potential deficiencies, sulfonated peat is undoubtedly useful as an ion exchange material.
Other common types of contaminants include organic materials, such as hydrocarbons, as well as phosphorous. Activated carbon has been found to be an effective medium for organic materials and phosphorous. While activated carbon can successfully remove undesirable materials from wastewater, activated carbon is quite expensive and requires processing to be useful as a filtering medium.
A variety of other specialized filtration mediums are available for treating contaminated water or other aqueous solutions. While these mediums may be highly effective in addressing certain treatment needs, they typically are quite expensive. Along these lines, there does not currently appear to be an inexpensive, integral medium capable of adsorbing toxic cations, organic materials, and phosphorous. Notably, the above-described rainwater or storm sewer runoff is but one example of an aqueous solution containing toxic cations, undesirable organic material, and especially phosphorous.
Perhaps due to the highly expensive nature of activated carbon and other applicable storm water treatment mediums, minimal efforts have been made to design a viable container for maintaining the treatment medium within a storm water sewer system. Regardless of the exact treatment material employed, the relatively harsh environment associated with a storm water sewer system places a number of constraints on the container not otherwise present in other filtration/treatment applications. For example, storm water entering the sewer system will often times includes a number of relatively large particles, such as grass clippings, that can block the entrance to the container. Additionally, contaminants removed from the storm water will accumulate within the container, potentially obstructing the container exit. Further, the volume and flow rate of water entering the storm sewer system (and thus the container) can vary greatly, especially during and following a heavy rainfall. It is quite possible that an increased volume and flow rate will exceed the capacity of the container/treatment media, possibly causing contaminated water to back-up within the container. Currently available treatment containers have not addressed these, and other constraints. For example, a flexible bag secured within the storm water sewer system below the sewer grate, while easy to install, will quickly become obstructed by the relatively large particles carried in the storm water. While other, more complex, devices are available, such as that described in U.S. Pat. No. 5,744,048 to Stetler, they are difficult to install and likely cost prohibitive.
Pollution control, and in particular treatment of contaminated water, continues to be an extremely important environmental concern. While various ion exchange and organic filtering materials are independently available to facilitate removal of toxic cations or organic contaminants from wastewater or other aqueous solutions, the costs associated with these materials are prohibitive. Further, there currently does not exist a storm water sewer system treatment container able to perform under the rigorous conditions presented by the sewer system on a cost effective basis. Therefore, a need exists for an inexpensive, filter canister for use within a storm water sewer system.
One aspect of the present invention provides a filter canister for use within a storm water sewer system. The filter canister includes a hollow retention body and a lower tapered filter. The retention body defines a top and a bottom and is positionable within a storm water sewer system to direct fluid flow from the top to the bottom. The lower tapered filter defines a vertex end and a base. The lower tapered filter is attached to the bottom of the retention body such that the vertex end extends upwardly toward the top. In one preferred embodiment, the filter canister contains a pelletized treatment medium, such as a peat-based product having activated carbon-like characteristics. In another preferred embodiment, the filter canister includes an upper tapered filter selectively secured to the top of the retention body such that a vertex of the upper tapered filter extends downwardly toward the bottom. Regardless, during use, the tapered shape and orientation of the lower tapered filter collects and directs various contaminants and other particles to location(s) that minimize any reduction in the volumetric flow through capacity of the filter canister.
Another aspect of the present invention provides a method of filtering effluent flowing into a storm water sewer system. The method includes providing a filter canister including a hollow retention body, a lower tapered filter, and a pelletized adsorbent media. The retention body defines a top and a bottom. The lower tapered filter is secured to the bottom of the retention body such that a vertex of the lower tapered filter extends upwardly toward the top. The pelletized adsorbent media is contained within the retention body. The filter canister is positioned within the storm water sewer system such that effluent entering the storm water sewer system flows into the top of the retention body. The effluent is directed through the retention body and into contact with the pelletized adsorbent media for removing contaminants from the effluent. The contaminants are guided to an outer periphery of the lowered tapered filter such that the contaminants minimally inhibit a flow rate of the effluent through the bottom of the retention body.